1. Field of the Invention
The present invention concerns a combustion chamber as described in the preamble of claim 1.
2. Discussion of Background
In view of the extremely low NO.sub.x emissions specified for gas turbine operation, many manufacturers are converting to the use of premixed burners. One of the disadvantages of premixed burners is that they go out even at very low excess air numbers (ratio of the actual air/fuel ratio to the stoichiometric air/fuel ratio), this occurring at a .lambda. of about 2, depending on the temperature after the gas turbine compressor. For this reason, such premixed burners must be supported by one or more pilot burners in part-load operation of a gas turbine. Generally speaking, diffusion burners are used for this purpose. Although this technique permits very low NO.sub.x emissions in the full-load range, the auxiliary burner system leads to substantially higher NO.sub.x emissions at part-load operation. The attempt, which has become known on various occasions, to operate the auxiliary diffusion burners with a weaker mixture or to use smaller auxiliary burners must fail because the burn-out deteriorates and the CO/C.sub.x H.sub.4 emissions increase very sharply. In the language of the specialist, this state of affairs has become known as the CO/C.sub.x H.sub.4 --NO.sub.x dilemma.